X-ray source and method for generating x-ray radiation

Abstract

The inventive concept relates to an X-ray source comprising a liquid target source configured to provide a liquid target moving along a flow axis, an electron source configured to provide an electron beam, and a liquid target shaper configured to shape the liquid target to comprise a non-circular cross-section with respect to the flow axis, wherein the non-circular cross-section has a first width along a first axis and a second width along a second axis, wherein the first width is shorter than the second width, and wherein the liquid target comprises an impact portion intersecting the first axis; wherein the X-ray source is configured to direct the electron beam towards the impact portion such that the electron beam interacts with the liquid target within the impact portion to produce X-ray radiation.

Description

[0001] This application is a divisional application of the application that entered the Chinese national phase on May 28, 2020, with application number 201880077013.5. Technical Field

[0002] The inventive concept described herein generally relates to an electron-impacted X-ray source, and specifically to a liquid target for use in such an X-ray source. Background Technology

[0003] Systems for generating X-rays by irradiating a liquid target are described in the applicant's international applications PCT / EP2012 / 061352 and PCT / EP2009 / 000481. In these systems, an electron gun, including a high-voltage cathode, is used to generate an electron beam that impinges on a liquid jet. The target is preferably formed of a low-melting-point liquid metal (such as indium, tin, gallium, lead, or bismuth, or alloys thereof) disposed within a vacuum chamber. The means for providing the liquid jet may include a heater and / or cooler, a pressurization device (such as a mechanical pump or a source of chemically inert propellant gas), a nozzle, and a container for collecting the liquid at the end of the jet. The X-ray radiation generated by the interaction between the electron beam and the liquid jet exits the vacuum chamber through a window that isolates the vacuum chamber from the surrounding atmosphere.

[0004] However, an improved X-ray source is still needed. Summary of the Invention

[0005] The purpose of this invention is to provide an improved X-ray source.

[0006] According to a first aspect of the invention, an X-ray source is provided, comprising: a liquid target source configured to provide a liquid target movable along a flow axis; an electron source configured to provide an electron beam; and a liquid target shaper configured to shape the liquid target into a non-circular cross-section with respect to the flow axis, wherein the non-circular cross-section has a first width along a first axis and a second width along a second axis, wherein the first width is shorter than the second width, and wherein the liquid target includes an impact portion intersecting the first axis; wherein the X-ray source is configured to guide the electron beam toward the impact portion such that the electron beam interacts with the liquid target within the impact portion to generate X-ray radiation; and wherein the X-ray source further includes means configured to move the position within the impact portion where the electron beam interacts with the liquid target.

[0007] The present invention is based on the understanding that by providing a non-circular cross-section for the liquid target, a wider impact surface for the electron beam can be achieved without increasing, for example, the flow rate of the liquid target. A wider or less curved impact surface also allows multiple electron beams (preferably along a direction perpendicular to the flow axis) to simultaneously impact the liquid target, and allows for the use of larger or wider electron beam spots without significantly affecting the focusing of the X-ray spot. It should be understood that such an impact surface can also be used with oval or even linear electron beam spots.

[0008] Furthermore, liquid targets with non-circular cross-sections can provide improved thermal performance compared to corresponding liquid targets with circular cross-sections of similar width and flow rate. Specifically, by reducing the width along one of the axes defining the cross-section of the liquid target, the velocity of the liquid target can be increased, which thus improves the thermal performance of the liquid target. In other words, the ability to heat-load a liquid target varies with the velocity of the liquid target. Maintaining velocity while increasing width implies increasing mass flow rate, which may in turn place higher demands on the pump system.

[0009] It is also desirable to be able to adjust the position of the impact portion relative to the position of the electron source and / or the X-ray window through which the X-ray radiation exits the X-ray source. Preferably, the impact portion and the electron source can be aligned such that the electron beam impacts the largest surface portion of the liquid target, i.e., the portion of the liquid target with the least curvature. Furthermore, it may be desirable to increase the width of the target at the impact portion to provide a larger surface area for the electron beam to impact.

[0010] Furthermore, it has been recognized that the incident angle of the electron beam impacting the liquid target can be important for, for example, the spatial distribution of the generated X-ray radiation. In particular, the incident angle and / or position of the electron beam impacting the liquid target can be selectively adjusted by rotating the first axis of the cross section about the direction of the electron beam, or vice versa, and / or by adjusting the position of the electron beam impacting the liquid target.

[0011] In the context of this application, the term 'width' can refer to the diameter or range of a liquid target from one side to the other. Specifically, the first width can be the maximum width of a non-circular cross-section along a first axis, and the second width can be the maximum width of a non-circular cross-section along a second axis. The first and second axes can be perpendicular to each other and can intersect the flow axis. The second width can be approximately 100 μm, for example, in the range of 10 μm to 1000 μm, such as 100 μm to 500 μm, or 150 μm to 250 μm. In some examples, the ratio between the second width and the first width can be at least 1.05, such as at least 1.1, at least 1.5, at least 2, or at least 5.

[0012] In the context of this application, the term 'liquid target' can refer to a liquid flow or stream forced through, for example, a nozzle and propagating through a system used to generate X-rays. While a liquid target can generally be formed from a substantially continuous liquid flow or stream, it should be understood that a liquid target may additionally or alternatively comprise or even be formed from multiple droplets. In particular, droplets can be generated upon interaction with an electron beam. Such examples of droplet groups or clusters can also be encompassed by the term 'liquid target'.

[0013] Liquid targets can have non-circular cross-sections, which can conform to oval, elliptical, or other elongated shapes. By making the cross-section more elongated, the curvature of the surface at the impact point can be reduced. Ultimately, the curvature can be low enough that the surface at the impact point approximates a flat two-dimensional surface. Such a target can also be called a 'flat jet'. In other words, the location of the impact point can be chosen as the part of the liquid target that most closely resembles a flat surface. A liquid curtain is an extreme example of such a jet, exhibiting a substantially flat surface at the impact point that can be used as an electron beam.

[0014] The liquid target can be formed by a liquid jet that propagates freely relative to the surrounding environment, at least at the location of the impact zone. The material of the liquid jet can therefore be exposed to the environment within the chamber of the X-ray source.

[0015] Typically, liquid target materials are metals, preferably with relatively low melting points. Examples of such metals include indium, gallium, tin, lead, bismuth, and their alloys.

[0016] As will be further described in the following disclosure, the electron beam spot can have a circular or elongated shape. In some examples, an elongated shape can also be implemented as a linear shape or a line focus. For a line focus, an aspect ratio, i.e., the ratio between the focal width and the focal height, can be defined. A typical aspect ratio achievable on a liquid target with a circular cross-section is 4. A larger aspect ratio can be achieved on a liquid target with a non-circular cross-section; for example, at least 6. The shape of the electron beam spot can be selected based on the preferred flux and / or brightness of the generated X-ray radiation.

[0017] To fully understand the following disclosures, it can be noted that for sufficiently large Weber numbers, a phenomenon known as axis switching can be observed for liquid targets flowing from nozzles with non-circular openings. Axis switching is a phenomenon in which the cross-section of a non-circular (e.g., elliptical) liquid target evolves such that the major and minor axes periodically switch positions along the flow direction of the liquid target. The wavelength of the switching increases with increasing liquid target velocity. Furthermore, axis switching is suppressed by viscosity, meaning that the amplitude of axis switching approaches zero as viscosity increases.

[0018] Therefore, it should be understood that the impact portion can extend along the flow axis. Further, the impact portion can be described as a section within a sector with a non-circular cross-section. This portion can, for example, span a sector with an angle of 180 degrees or less (e.g., 120 degrees or less, 90 degrees or less, 60 degrees or less), and can preferably be centered on the first axis.

[0019] The X-ray source can be further configured to guide the electron beam toward a specific region within the impact portion. Such a region can also be referred to as the interaction region. Therefore, the impact portion can be understood as the part intersecting the first axis (e.g., a surface portion or volume), while the interaction region can be understood as a specific portion or area of ​​the impact portion that is struck by the electron beam and in which X-ray radiation can be generated. The interaction region can be a volume extending a distance toward the center of a non-circular cross-section (i.e., toward the flow axis). Similarly, the impact portion can be a volume that extends a distance toward the center of a non-circular cross-section (i.e., toward the flow axis).

[0020] As can be readily understood from this disclosure, the device can be configured to adjust the position of the electron beam impacting the liquid target, or in other words, the position of the interaction zone. This may be necessary to ensure that the entire size of the electron beam spot interacts with the liquid target, and in particular to ensure that the electron beam spot interacts with the liquid target within the impact region.

[0021] The device may, for example, include electro-optical devices for moving the electron beam relative to the liquid target. Alternatively or additionally, the device may be configured to cooperate with a liquid target shaper to move or adjust the position where the electron beam interacts with the target. In an example, the device may include a motor or actuator coupled to the liquid target shaper and arranged to move the target shaper in a manner that allows adjustment of the position or orientation of the liquid target. The device may, for example, be configured to rotate the liquid target shaper about a flow axis, thereby causing a corresponding rotation of the impact portion about the flow axis, such that the orientation and / or position of the impact portion relative to the electron source may change. In a further example, the device may be configured to translate the liquid target shaper in a direction orthogonal to the flow axis and / or the trajectory of the electron beam, and / or tilt the liquid target shaper relative to the flow axis.

[0022] In one example, the device can be configured to control a magnetic field generator, which is configured to generate a magnetic field to shape a liquid target into a non-circular cross-section. The magnetic field generator will be described in more detail below.

[0023] The above disclosure provides several examples of how this apparatus can be used to adjust the relative position between the electron beam and the liquid target. Moving the interaction zone and / or impact portion may result in adjustment of the incident angle of the electron beam. The purpose of making such modifications may be to increase the total X-ray flux along the viewing direction or at a sample location, increase the brightness of the X-ray source, or align the position of the X-ray source with other components of the X-ray system (e.g., optics). In the examples, the adjustment of the incident angle and / or the position of the interaction zone is based on the measured X-ray output.

[0024] An electron beam can interact with the impactor at an incident angle greater than 0 degrees. The incident angle can be defined as the angle of incidence relative to the normal to the non-circular cross-section.

[0025] The advantage of having the electron beam interact with the impactor at an incident angle greater than 0 degrees is that less X-rays are absorbed in the liquid target. Specifically, more X-rays can be transmitted via an X-ray window positioned at an angle (e.g., substantially perpendicular) to the direction of the electron beam. Therefore, this device can provide increased total X-ray flux and / or increased X-ray brightness.

[0026] In the following text, possible modifications to the X-ray source will be described in particular to allow for adjustment of the incident angle and / or the position of the electron beam striking the interaction zone of the liquid target. As will be understood from the following paragraphs, modifications can be made to the liquid target, the electron beam, or a combination of both.

[0027] The electron source can be configured to rotate about the flow axis in order to adjust the incident angle of the electron beam and / or the position of the electron beam in the interaction zone where it strikes the target.

[0028] The liquid target shaper may include a nozzle with a non-circular opening to shape the liquid target into a non-circular cross-section. The opening may, for example, have a shape selected from the group consisting of: ellipse, rectangle, square, hexagon, egg, stadium, and rectangle with rounded corners.

[0029] It should be understood that, according to some embodiments, the X-ray source can be configured to move the liquid target relative to the electron beam, thereby altering the position where the electron beam interacts with the liquid target. This movement can be achieved, for example, in a direction perpendicular to the flow axis of the liquid jet and / or perpendicular to the propagation direction of the electron beam, resulting in a lateral shift in the position of the interaction region. The movement or position shift of the interaction region can be achieved, for example, by means of the liquid target source.

[0030] In one example, the nozzle of the liquid target source can be configured to move along the flow axis in order to adjust the incident angle and / or the position of the interaction zone.

[0031] In one example, the nozzle can be configured to rotate about the flow axis in order to adjust the incident angle and / or the position of the interaction zone.

[0032] In one example, the liquid target source can be configured to move in a direction perpendicular to the flow axis in order to adjust the incident angle and / or the position of the interaction zone.

[0033] The liquid target shaper may include a magnetic field generator configured to generate a magnetic field to shape the liquid target into a non-circular cross-section. The magnetic field may be substantially perpendicular to the flow axis. The amplitude of the magnetic field may be non-uniform in the direction of the flow axis, causing the liquid target to experience a field gradient as it travels along the flow axis. In other words, the magnetic field may include a magnetic field gradient. The mechanism for shaping the liquid target may be based on induced eddy currents within the liquid target, thus the liquid target may be conductive. The magnetic field may be an alternating magnetic field.

[0034] Examples could include a time-varying component of a magnetic field oriented along the flow axis. This field component can impart acceleration to the liquid target, thus increasing the thermal load that can be applied to the liquid target before vaporization or similar problems occur.

[0035] By applying a magnetic field gradient, the maximum relative change in the radius of the liquid target can be written as:

[0036]

[0037] in,

[0038] β=ε m N α / 8α, ε m =α / L m

[0039] and

[0040]

[0041] N as defined above a This is called the Stuart number, We is the Weber number, α is the nozzle radius, B0 is the amplitude of the magnetic field, and L... m Let be the length scale of the magnetic field gradient, and σ e The conductivity of the liquid target.

[0042] In one example, the liquid target is composed of liquid gallium, and the following values ​​are input into the formula above:

[0043] ρ=6100kg / m 3 ,

[0044] σ=0.7N / m,

[0045] α = 100 μm,

[0046] v = 100 m / s,

[0047] σ e =4MS / m,

[0048] B0 = 1.7T, and

[0049] L m =1mm,

[0050] This could cause the maximum change in the radius of the liquid target to reach several percent.

[0051] Similar to the case of an elliptical nozzle, the shape of the liquid target may oscillate along the flow axis. The values ​​used above give a wavelength of approximately 250 times the nozzle radius, or 25 mm. If the exit velocity of the liquid target increases to 1000 m / s (i.e., the Weber number increases by a factor of 100), the amplitude remains approximately the same, but the wavelength increases by a factor of 10. Since the amplitude is proportional to the Stewart number (i.e., proportional to the square of the magnetic field), one way to increase the amplitude of the relative radius change is to increase the magnetic field. Another way to increase the effect is to increase the Weber number. This can be done by reducing the surface tension without affecting the Stewart number. This can then be achieved by increasing the temperature. As an example, by increasing the magnetic field to 4 T, the effect amplitude of the relative radius change is approximately 10%. Incidentally, this amplitude may also increase with increasing the nozzle diameter. However, as discussed above, this may be counterproductive, as simply increasing the diameter while maintaining the mass flow rate may result in a lower velocity. A lower velocity, in turn, may mean a lower permissible thermal load on the liquid target.

[0052] The magnetic field generator can be configured to adjust the magnetic field in order to adjust the incident angle and / or the position of the interaction region.

[0053] The magnetic field can be non-uniform. In particular, the magnetic field generator can be configured to adjust the direction of the non-uniform magnetic field in order to adjust the angle of incidence and / or the position of the interaction region.

[0054] In one example, the magnetic field generator can be configured to generate a magnetic field that moves the liquid target, causing the position of the interaction region to shift relative to the electron beam.

[0055] The liquid target source can be configured to provide an adjustable flow rate of the liquid target in order to adjust the first width and the second width.

[0056] Liquid targets can be metal.

[0057] The X-ray source can be configured to rotate the impact region about the direction of the electron beam. In other words, the X-ray source can be configured to rotate the first axis of the non-circular cross-section about the direction of the electron beam.

[0058] It should be understood that, according to the present invention, both the nozzle and the magnetic field generator described above can be present in the X-ray source.

[0059] According to a second aspect of the invention, a method for generating X-ray radiation is provided. The method includes: providing an electron beam; providing a liquid target movable along a flow axis, the liquid target including a non-circular cross-section about the flow axis, wherein the non-circular cross-section has a first width along a first axis and a second width along a second axis, wherein the first width is shorter than the second width, and wherein the liquid target includes an impact portion intersecting the first axis; and guiding the electron beam toward the impact portion such that the electron beam interacts with the liquid target within the impact portion to generate X-ray radiation.

[0060] The method may further include moving the electron beam along the flow axis and / or in a direction perpendicular to the flow axis to move the position where the electron beam interacts with the liquid target, i.e., the interaction region.

[0061] The method may further include rotating the electron source about the flow axis to adjust the incident angle and / or the position of the interaction region.

[0062] The method may further include moving the nozzle along the flow axis to adjust the incident angle and / or the position of the interaction zone.

[0063] The method may further include rotating the nozzle about the flow axis to adjust the incident angle and / or the position of the interaction zone.

[0064] The step of providing a liquid target may include providing a magnetic field for shaping a non-circular cross-section of the liquid target.

[0065] The method may further include adjusting the magnetic field in order to adjust the incident angle and / or the position of the interaction region.

[0066] The method may further include adjusting the flow rate of the liquid target in order to adjust the first width and the second width.

[0067] The method may further include rotating the impact region about the direction of the electron beam.

[0068] The method may further include the step of scanning an electron beam between a liquid target and an uncovered portion of the sensor region to determine, for example, the width of the electron beam (preferably the width at the impact portion). A sensor region, which may form part of an X-ray source according to the first aspect, may be arranged behind the liquid target (from the view of the electron source) such that the liquid target at least partially covers the sensor region. This arrangement allows the electron beam to be scanned into and / or out of the liquid target and impact(s) the uncovered portions(s) of the sensor region. The output signal from the sensor can then be analyzed to determine the width of the liquid target (preferably the width in the scanning direction or in a direction perpendicular to the flow axis).

[0069] The determined width of the liquid target can be used as a feedback or adjustment parameter for operating the liquid target source, liquid target shaper, and / or electron beam. The purpose of this feedback or adjustment can be to control the width of the liquid target (preferably at the impact portion). Therefore, this width can be changed by adjusting the flow rate of the liquid target, by rotating the impact portion about the flow axis, by moving the position where the electron beam interacts with the liquid target, and / or by adjusting the incident angle between the electron beam and the surface of the impact portion.

[0070] In one example, the method according to the second aspect may include measuring X-ray output, such as X-ray flux and / or X-ray luminance. The measurement can be performed using a sensor device for characterizing or quantifying the generated X-ray radiation. Similar to the feedback mechanism described above, the measured X-ray output can be used to control the interaction between the electron beam and the liquid target to achieve a desired output (e.g., in terms of flux or luminance). For example, the interaction can be controlled by rotating the impact portion about a flow axis, moving the position where the electron beam interacts with the liquid target, or adjusting the angle of incidence between the electron beam and the surface of the impact portion.

[0071] The feature described in the first aspect of the above-mentioned aspects can also be incorporated into the other aspect of the above-mentioned aspects, and the advantages of the feature are applicable to all aspects incorporating the feature.

[0072] Other objectives, features and advantages of the present invention will become apparent from the following detailed disclosure, from the appended claims and from the accompanying drawings.

[0073] Generally, unless otherwise expressly defined herein, all terms used in the claims shall be interpreted according to their ordinary meaning in the art. Furthermore, the use of the terms “first,” “second,” and “third,” etc., herein does not indicate any order, quantity, or importance, but is used to distinguish one element from another. Unless otherwise expressly stated, all references to “an / a / the [element, device, component, apparatus, step, etc.]” ​​shall be interpreted openly as referring to at least one instance of said element, device, component, apparatus, step, etc. Unless expressly stated otherwise, the steps of any method disclosed herein do not necessarily have to be performed in the exact order disclosed. Attached Figure Description

[0074] Referring to the accompanying drawings, the above and additional objects, features, and advantages of the inventive concept will be better understood through the following illustrative, rather than limiting, detailed description of various embodiments thereof, in which:

[0075] Figure 1a An X-ray source is shown schematically;

[0076] Figure 1b An X-ray source equipped with a magnetic field generator is shown schematically.

[0077] Figure 2 A perspective view of the liquid target is shown schematically;

[0078] Figure 3 The diagram illustrates a non-circular cross-section of a liquid target.

[0079] Figures 4a to 4b The movement of the electron source is schematically shown in order to adjust the incident angle and / or the position of the interaction region;

[0080] Figure 4c The diagram schematically illustrates the non-circular cross-section of a liquid target being bombarded by multiple electron beams.

[0081] Figure 4d An electron beam with a slender cross-section is schematically shown.

[0082] Figures 5a to 5b The schematic diagram illustrates the shaping of a liquid target to adjust the incident angle and / or the position of the interaction zone;

[0083] Figures 6a to 6b The movement of the electron beam is schematically shown in order to adjust the incident angle and / or the position of the interaction region;

[0084] Figure 7 This is a flowchart of a method for generating X-ray radiation.

[0085] These figures are not necessarily drawn to scale and generally only show the parts necessary to illustrate the inventive concept, while other parts may be omitted or are merely suggested. Detailed Implementation

[0086] Now refer to Figure 1a An X-ray source according to the present invention is described. An electron beam 100 is generated from an electron source 102 (e.g., an electron gun including a high-voltage cathode), and a liquid target 104 is provided from a liquid target source 106. The electron beam 100 is guided toward the impact portion of the liquid target 104, such that the electron beam 100 interacts with the liquid target 104 and generates X-ray radiation 108. Preferably, the liquid target 104 is collected by means of a pump 110 (e.g., a high-pressure pump) and returned to the liquid target source 106, the high-pressure pump being adapted to increase the pressure to at least 10 bar (preferably to at least 50 bar) to generate the liquid target 104.

[0087] The liquid target 104 (i.e., the anode) can be formed by a liquid target source 106 including a nozzle through which a fluid such as liquid metal or liquid alloy can be ejected to form the liquid target 104. It should be noted that it should be understood that X-ray sources including multiple liquid targets and / or multiple electron beams are possible within the scope of the inventive concept.

[0088] Still referencing Figure 1a The X-ray source may include an X-ray window (not shown) configured to allow transmission of X-ray radiation generated by the interaction between the electron beam 100 and the liquid target 104. The X-ray window may be positioned substantially perpendicular to the direction of travel of the electron beam.

[0089] Now for reference Figure 1b The diagram illustrates a magnetic field generator 103 in relation to a liquid target source 106 and a liquid target 104. The magnetic field generator 103 and the liquid target 104 can be included in an X-ray source, which can be similarly configured to combine... Figure 1a The X-ray source under discussion. It should be understood that the magnetic field generator 103 may extend further along the flow axis, and the placement of the magnetic field generator 103 shown is merely an example among several different configurations. In this example, the magnetic field generator 103 may include a plurality of means for generating magnetic fields for modifying or shaping the cross-section of the liquid target 104. Examples of such means may include, for example, electromagnets, which may be arranged, for example, on different sides of the path of the liquid target 104 to influence the shape of the liquid target.

[0090] Now for reference Figure 2 An example of a liquid target 204 moving along a flow axis F is shown. The liquid target is generated by a liquid target source 206. The X-ray source includes a liquid target shaper, such as a nozzle 212 with a non-circular opening, to shape the liquid target 204 into a non-circular cross-section 214. In the example shown, the nozzle 212 has an elliptical opening. The non-circular cross-section 214 has a first width (also referred to as diameter) along a first axis A1 and a second width or diameter along a second axis A2, wherein the first diameter is shorter than the second diameter. The liquid target 204 includes an impact portion 216 intersecting the first axis A1. Here, the impact portion 216 is shown as a uniform region centered on the first axis A1. However, it should be understood that the impact portion 216 can have any arbitrary shape. Furthermore, it should be noted that the impact portion 216 is shown here only as a non-circular cross-section, but the impact portion 216 can extend along the flow axis F.

[0091] Electron beam 200 is directed toward impact region 216, causing it to interact with liquid target 204 and generate X-ray radiation. Specifically, electron beam 200 is directed to interaction region 218 located within impact region 216. Interaction region can be defined as the area in which X-rays are generated when struck by electron beam.

[0092] As previously discussed in this disclosure, axis switching can be observed depending on the performance of the liquid target 204. Figure 2 In the diagram, the first and second axes can be observed switching positions along the flow axis F. The axes of the liquid target 204 (i.e., the first axis A1 and the second axis A2) can switch positions multiple times along the flow axis F, with the wavelength proportional to the velocity of the liquid target along the flow axis F. Specifically, the wavelength of the axis switching is proportional to the square root of the Weber number, which corresponds to a linear velocity dependence. For certain parameter combinations, it is possible to observe a situation where only one axis switching event occurs; for example, the liquid target ejected from the elongated nozzle rotates 90 degrees and then continues without flipping the observable distance.

[0093] Now for reference Figure 3 The non-circular cross-section 314 is shown in detail. The non-circular cross-section 314 can be formed in conjunction with the above figures 1 and 2. Figure 2 This is a portion of the liquid target of those similar X-ray sources discussed. It should be noted that the interaction region 318 in this figure is not necessarily drawn to scale. The non-circular cross-section 314 includes a first diameter 322 along a first axis A1 and a second diameter 320 along a second axis A2, wherein the first diameter 322 is shorter than the second diameter 320. As can be seen, the impact portion 316 intersects the first axis A1. Here, the electron beam 300 interacts with the liquid target at an incident angle θ greater than 0 degrees.

[0094] Now for reference Figure 4a Electron beam 400 is shown interacting with liquid target 404 at an incident angle θ1. Interaction region 418 is located within impact portion 416. To adjust the incident angle and / or the position of interaction region 418, the electron source (not shown) providing electron beam 400 can be rotated about the flow axis. Figure 4b As shown, this rotation can cause the electron beam 400 to interact with the liquid target 404 at an incident angle θ2, and the position of the interaction region 418 can also be changed within the impact portion 416.

[0095] Now for reference Figure 4cA first electron beam 400 and a second electron beam 401 are shown interacting with a liquid target 404. Corresponding first interaction regions 418 and 419 are shown. The first and second interaction regions 418 and 419 are arranged within an impact portion 416. X-ray radiation 408 generated in the first interaction region 418 is transmitted through a first X-ray window 421 positioned substantially perpendicular to the first electron beam 400. X-ray radiation 409 generated in the second interaction region 419 is transmitted through a second X-ray window 423 positioned substantially perpendicular to the second electron beam 401. As can be seen, the X-ray radiation can preferably be transmitted via an X-ray window positioned in a direction pointing away from a first axis with respect to a non-circular cross-section of the interaction region in which the X-ray radiation is generated. This is to avoid damping of the X-ray radiation caused by absorption in the liquid target.

[0096] Now for reference Figure 4d An electron beam 400 with an elongated cross-section is shown. As can be seen in the shown cross-section, the interaction region 418 located within the impact portion 416 can therefore be elongated or linear in shape. According to the invention, when using an electron beam 400 with an elongated cross-section, it may be advantageous to guide the electron beam 400 toward the impact portion in order to achieve improved focusing performance. Furthermore, X-ray radiation generated in the interaction region 418 can be transmitted via X-ray windows located on either or both sides of the first axis.

[0097] Now for reference Figure 5a An electron beam 500 is shown interacting with a liquid target 504 at an incident angle θ1. An interaction region 518 is located within the impact portion 516. To adjust the incident angle and / or the position of the interaction region 518, the liquid target 504 can be rotated about a flow axis. This can be achieved, for example, by rotating a nozzle about a flow axis, and / or by adjusting the arrangement to shape the liquid target 504 into a magnetic field comprising a non-circular cross-section. Figure 5b As shown, the rotation of the liquid target 504 around the flow axis can cause the electron beam 500 to interact with the liquid target 504 at an incident angle θ2, and the position of the interaction region 518 can also be changed within the impact portion 516.

[0098] Now for reference Figure 6aAn electron beam 600 is shown interacting with a liquid target 604 at an incident angle θ1. Here, θ1 is essentially zero. The interaction region 618 is located within the impact portion 616. To adjust the incident angle and / or the position of the interaction region 618, the electron beam 600 can be moved along the flow axis and / or in a direction perpendicular to the flow axis. The example shown illustrates the movement of the electron beam 600 in a direction perpendicular to the flow axis. The movement of the electron beam 600 along the flow axis and / or in a direction perpendicular to the flow axis can be achieved by having an electro-optical device (not shown) configured to move the electron beam 600. The term "movement" should be interpreted to include focusing and / or deflecting the electron beam. Figure 6b As shown, moving the electron beam 600 as disclosed above can cause the electron beam 600 to interact with the liquid target 604 at an incident angle θ2, and the position of the interaction region 618 can also be changed within the impact portion 616.

[0099] Furthermore, although not shown, the nozzle of the liquid target former can be moved along the flow axis, and / or the magnetic field generated by the magnetic field generator can be adjusted to regulate the incident angle and / or the position of the interaction zone. The resulting adjustment of the incident angle and / or the position of the interaction zone is similar to the combination described above. Figures 4a to 6b The disclosed adjustments.

[0100] Furthermore, it should be understood that the above combination Figures 4a to 6b Any combination of the disclosed modifications is possible within the scope of the inventive concept.

[0101] The above combination can be performed by providing a suitable sensor device and controller (not shown). Figures 4a to 6b The disclosed adjustments are designed to achieve the desired performance. One example is providing increased X-ray flux at the sample location, measured in the number of X-ray photons per second. Another example is providing increased X-ray luminance, i.e., the number of photons per time, per area, and per solid angle. To measure luminance, a detector capable of recording the spatial distribution of X-ray radiation intensity may be required. The adjustments can be controlled using appropriate control algorithms, such as PID controllers.

[0102] As previously combined Figure 4cThe X-ray source mentioned can include more than one electron beam, thus providing more than one interaction region. An example of this would be a two-port source, i.e., a situation where two X-ray windows exist in opposite directions substantially perpendicular to two substantially parallel electron beams. With such a device, the two spots can be individually tuned to achieve the desired performance. Another example is providing multiple X-ray sources radiating in the same direction for interferometric applications (e.g., Talbot-Lau interferometry). In this context, it can be noted that a wide target may be preferred because the thermal load can be distributed across the width, with multiple spots distributed substantially perpendicular to the flow axis interacting with the liquid target. Alternatively, if the spots are arranged along the flow axis, the permissible thermal load will be smaller because the downstream interaction region will also be exposed to the thermal load of the upstream interaction region.

[0103] Now refer to Figure 7 A method for generating X-ray radiation according to the present invention is described. For clarity and simplicity, the method will be described in terms of 'steps'. It should be emphasized that the steps are not necessarily time-defined or separate processes, and more than one 'step' can be performed simultaneously in parallel.

[0104] In step 724, a liquid target is provided that moves along the flow axis. In step 726, an electron beam is provided. In step 728, the liquid target is shaped to include a non-circular cross-section about the flow axis, wherein the non-circular cross-section includes a first diameter shorter than a second diameter, and wherein the liquid target includes an impact portion intersecting the first axis. In step 730, the electron beam is directed toward the impact portion such that the electron beam interacts with the liquid target within the impact portion to generate X-ray radiation.

[0105] The method may further include steps for adjusting the impact portion to provide a wider impact portion for the electron beam to interact with. The width of the liquid target can be measured by scanning the electron beam across the liquid target at 732 and measuring the current absorbed in an electron accumulator (e_dump) (not shown) located downstream of the liquid target in the direction of the electron beam. The method may further include steps for oriented the width toward a desired value control 734.

[0106] Alternatively or additionally, the method may include the following steps: measuring 736 X-ray output such as X-ray flux or X-ray brightness, and controlling 738 the generation of X-ray radiation based on the measured X-ray output.

[0107] Those skilled in the art will not be limited to the exemplary embodiments described above. Rather, numerous modifications and variations are possible within the scope of the appended claims. In particular, within the scope of the inventive concept, X-ray sources and systems comprising more than one liquid target are contemplated. Furthermore, X-ray sources of the type described herein can be advantageously combined with X-ray optics and / or detectors tailored to a particular application, such as, but not limited to, medical diagnostics, nondestructive testing, photolithography, crystal analysis, microscopy, materials science, microscopic surface physics, X-ray diffraction for protein structure determination, X-ray spectroscopy (XPS), critical-size small-angle X-ray scattering (CD-SAXS), and X-ray fluorescence spectroscopy (XRF). Additionally, variations of the disclosed examples can be understood and implemented by those skilled in the art in practicing the claimed invention by studying the drawings, disclosure, and appended claims. The mere fact that certain measures are referenced in mutually different dependent claims does not indicate that combinations of these measures cannot be used advantageously.

[0108] List of reference numerals

[0109] 100 electron beam

[0110] 102 Electronic Source

[0111] 103 Magnetic Field Generator

[0112] 104 Liquid Target

[0113] 106 Liquid Target Source

[0114] 108 X-ray radiation

[0115] 110 pump

[0116] 200 electron beam

[0117] 204 Liquid Target

[0118] 206 Liquid Target Source

[0119] 212 Nozzle

[0120] 214 Non-circular cross-section

[0121] 216 Impact section

[0122] 218 Interaction Region

[0123] 300 electron beam

[0124] 314 Liquid Target

[0125] 316 Impact section

[0126] 318 Interaction Region

[0127] 320 Second Width

[0128] 322 First Width

[0129] 400 First Electron Beam

[0130] 401 Second Electron Beam

[0131] 404 Liquid Target

[0132] 408 X-ray radiation

[0133] 409 X-ray radiation

[0134] 416 Impact section

[0135] 418 First Interaction Region

[0136] 419 Second Interaction Region

[0137] 421 First X-ray window

[0138] 423 Second X-ray window

[0139] 500 electron beam

[0140] 504 Liquid Target

[0141] 516 Impact section

[0142] 518 Interaction Region

[0143] 600 electron beam

[0144] 604 Liquid Target

[0145] 616 Impact section

[0146] 618 Interaction Region

[0147] 724 Steps for providing a liquid target

[0148] 726 Steps for providing an electron beam

[0149] 728 Steps for shaping a liquid target

[0150] 730 Steps for guiding the electron beam

[0151] 732 Steps for Scanning Electron Beams

[0152] 734 Steps to control width

[0153] 736 Steps for measuring X-ray output

[0154] 738. Steps for controlling X-ray output.

Claims

1. An X-ray source, comprising: A liquid target source configured to provide a liquid target that moves along a flow axis by injecting liquid through a nozzle of the liquid target source; An electron source, configured to provide an electron beam; as well as A liquid target shaper is configured to shape a liquid target into a non-circular cross-section in a plane perpendicular to the flow axis, wherein the non-circular cross-section has a first width along a first axis and a second width along a second axis, wherein the first width is shorter than the second width, and wherein the liquid target includes an impact portion intersecting the first axis. The X-ray source is configured to guide the electron beam toward the impact portion in the form of a line focal point with an aspect ratio of at least 6, such that the electron beam interacts with the liquid target within the impact portion to generate X-ray radiation; and The X-ray source further includes: A device configured to move the position where the electron beam interacts with the liquid target within the impact portion; A pump suitable for increasing the pressure in a liquid target source to at least 50 bar to generate a liquid target.

2. The X-ray source according to claim 1, wherein, The second width is at least 150 μm.

3. The X-ray source according to claim 1, wherein, The second width is at least 500 μm.

4. The X-ray source according to claim 1, wherein, The second width is in the range of 150μm to 1000μm.

5. The X-ray source according to claim 1, wherein, The second width is in the range of 250μm to 1000μm.

6. The X-ray source according to claim 1, wherein, The second width is in the range of 500μm to 1000μm.

7. The X-ray source according to claim 1, wherein, The ratio between the second width and the first width is at least 5.

8. The X-ray source according to claim 1, wherein, The nozzle has a non-circular opening so that the liquid target is shaped to include a non-circular cross section.

9. The X-ray source according to claim 8, wherein, The non-circular opening has a shape selected from the group consisting of: ellipse, rectangle, square, hexagon, egg, stadium shape, and rectangle with rounded corners.

10. The X-ray source according to claim 1, wherein, The liquid target shaper includes a magnetic field generator configured to generate a magnetic field for shaping the liquid target into a shape including the non-circular cross-section.

11. The X-ray source according to claim 1, wherein, The liquid is metallic.

12. The X-ray source according to claim 1, wherein, The liquid is an alloy.

13. A method for generating X-ray radiation, the method comprising: Provide electron beam; A liquid target that moves along a flow axis is provided by spraying liquid through a nozzle. The liquid target includes a non-circular cross-section in a plane perpendicular to the flow axis, wherein the non-circular cross-section has a first width along a first axis and a second width along a second axis, wherein the first width is shorter than the second width, and wherein the liquid target includes an impact portion intersecting the first axis. The electron beam is guided toward the impact portion in the form of a line focal point with an aspect ratio of at least 6, such that the electron beam interacts with the liquid target within the impact portion to generate X-ray radiation; and The position where the electron beam interacts with the liquid target is moved within the impact section; The liquid is injected through a nozzle at a pressure of at least 50 bar.

14. The method according to claim 13, wherein, The second width is at least 150 μm.

15. The method according to claim 13, wherein, The second width is at least 500 μm.

16. The method according to claim 13, wherein, The second width is in the range of 150μm to 1000μm.

17. The method according to claim 13, wherein, The second width is in the range of 250μm to 1000μm.

18. The method according to claim 13, wherein, The second width is in the range of 500μm to 1000μm.

19. The method according to claim 13, wherein, The ratio between the second width and the first width is at least 5.

20. The method according to claim 13, wherein, The nozzle has a non-circular opening so that the liquid target is shaped to include a non-circular cross section.

21. The method according to claim 13, wherein, The liquid is metallic.

22. The method according to claim 13, wherein, The liquid is an alloy.

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